Monitoring the Mixing Process With ERT
The mixing process is a vital stage in manufacturing and is used prominently throughout the chemicals, FMCG and dairy industries. The challenge of industrial mixing is to regulate the volume of ingredients entering the mixing tavern and to reduce cycle times by avoiding over mixing, whilst continuously maintaining product consistency.
To combat these challenges ITS has develop the MIX-ITOMETER. The MIX-ITOMETER uses Electrical Resistance Tomography (ERT) to measure average concentration and mixing index by surveying more than 200 locations inside the process vessel. The data acquisition system can then process this data to provide a visual representation of the current mixing in real time using a PC interface.
Our system was recently put to the test in a trial, with a leading painting and coating manufacturer, to monitor the mixing of surface coatings. The production of surface coatings is particularly tricky, as it involves a number of variables which are introduced whilst mixing – such as the addition of pigments, binders and solvents, the use of different impellers and changes in operating speed.
The tests monitored changes to the surface coating formulation during each mixing stage; to do this 4 planes of 16 electrodes were equally distributed around the periphery of a 7 litre sensing vessel; thus applying a typical measuring protocol of 104 individual voltage measurements per plane.
ERT provides data in the form of voltage measurement. A sudden spike or drop represents a change in conductivity caused by new substances entering the mixing cavern; this is highlighted on the graph below – which has been taken directly from the trial data. In this example the pigments (and other powdered material) are entering the mixing vessel; which leads to a sharp increase on the graphs trajectory. As the mixing progresses the line begins to stabilise which informs us that the product is reaching a homogenous state.
The above graph is a snippet from the overall mixing; analysis of the complete findings display that effective mixing was achieved at the end of each stage of production. These results verify the MIX-ITOMETER as a system which can be used to overcome the challenges of mixing by giving users greater control over product consistency, processing efficiency and yield measurement.